Definition A.2 (Definition 15.4 in [1]}) 
A tetrahedron \(T=\langle v_{1},v_{2},v_{3}, v_{4}\rangle \)  with \(\lbrace v_i:=(x_i, y_i, z_i)\rbrace _{i=1}^4\)  is nondegenerate provided that it has nonzero volume, and the vertices of \(T\)  are in canonical order provided that if we rotate and translate \(T\)  so that the triangular face \(\langle v_{1},v_{2},v_{3}\rangle \)  lies in the \(xy\) -plane with \(v_{1},v_{2},v_{3}\)  in counterclockwise order, then \(z_4>0\) .

